1. Field of the Invention
The present invention relates to a manufacturing method of a composite material of a nanoparticle of a metal oxide having any of Fe, Ni, Co or Mn, with conductive carbon powder.
2. Description of the Related Art
A composite material that contains a metal oxide and conductive carbon is widely utilized in the field such as a fuel battery, a secondary battery, an electrochemical capacitor, or an antistatic material. Especially, a compound oxide of a transition metal such as Mn, Ni, Co or Fe and a typical metal belonging to group 1 or 2 in the periodic table such as Li or Mg is expected to be a positive electrode active material of a secondary battery such as a lithium ion secondary battery or a magnesium ion secondary battery, and composite materials of the compound oxide with conductive carbon have been frequently considered.
These composite materials are generally manufactured by a method to mix a metal oxide particle and conductive carbon powder or by a method to support a prepared metal oxide on conductive carbon powder during a production process for the metal oxide.
For example, Patent Document 1 (JP H2-109260 A) discloses a positive electrode of a lithium ion secondary battery in which LiMn2O4, which is obtained by dissolving a lithium source such as lithium nitrate or lithium hydroxide in water, adding manganese nitrate as a manganese source to the solution, and giving heat treatment to the solution, is mixed with a conductive agent such as acetylene black and pressure-formed. Also, Patent Document 2 (JP 2005-63677 A) discloses an electrode catalyst of a fuel battery that is manufactured by mixing powder of a metal oxide such as manganese oxide, cobalt oxide or nickel oxide and a conductive agent such as conductive carbon black powder and coating the mixture obtained on a conductive porous substrate.
As a method to support a prepared metal oxide on conductive carbon powder in a formation process for the metal oxide, the applicant has proposed in Patent Document 3 (JP 2007-160151 A) a reaction method to promote chemical reaction by adding shear stress and centrifugal force to a reactant in a turning reactor. This document shows that a composite material, in which a nanoparticle of an oxide such as titanium oxide or ruthenium oxide is supported on conductive carbon powder in a highly dispersed state by a sol-gel reaction accelerated by addition of shear stress and centrifugal force, is suitable for a positive electrode or a negative electrode of a battery or an electrochemical capacitor.